The disclosure relates to an image-recording device having a recording head for ejecting ink droplets, a carriage that reciprocates in a linear direction and supports the recording head, ink supply tubes for supplying ink to the recording head from ink tanks, and a flat cable connected to the carriage for transmitting a recording signal thereto.
One type of conventional image-recording device records images on a recording medium by ejecting ink based on an input signal. One such image-recording device well known in the art provides ink to an actuator in a recording head and ejects the ink in droplets using pressure generated by the actuator based on the input signal. Here, the actuator may be a piezoelectric element, electrostriction element, or the like that generates pressure by flexing the element, or by boiling the ink locally with heating elements.
One of these image-recording devices disclosed in Japanese patent application publication No. HEI-6-320835 is a serial printer with the recording head mounted on a carriage that reciprocates in a linear direction orthogonal to the conveying direction of the recording paper. The serial printer records images by scanning the carriage each time the recording paper is conveyed by the amount of a prescribed line feed. A flexible cable called a flat cable is connected to the carriage to control the same. The flat cable must have sufficient length to follow the reciprocating motion of the carriage without interfering with that motion. The cable is disposed between the carriage and a main circuit board or the like and is bent substantially in a U-shape.
Another such image-recording device disclosed in U.S. Pat. No. 6,755,514 (corresponding to Japanese patent application publication No. 2003-175588) attempts to reduce the size of the carriage on which the recording head is mounted by providing ink tanks separately from the carriage and supplying ink to the carriage via ink supply tubes in order to lighten the load on a motor and the like used to drive the carriage. Further, this technology can reduce the overall height of the device by running the ink supply tubes laterally from the carriage in the moving direction of the carriage rather than from the top of the carriage.
FIG. 22 shows an example of a conventional image-recording device having a carriage 90 and a flat cable 91. The carriage 90 reciprocates in a direction (left-and-right direction in FIG. 22) orthogonal to the conveying direction for the recording paper, while a recording head (not shown) mounted in the carriage 90 ejects ink droplets to form images on the recording paper. The flat cable 91 is connected to the carriage 90 in order to transmit and receive electric signals between the main circuit board and the carriage 90. The flat cable 91 has an end 92 that is fixed to a frame or the like (not shown) of the image-recording device and that is electrically connected to the main circuit board. Although not shown in FIG. 22, the carriage 90 is supported on a guide rail and reciprocates by a drive force applied by a belt drive mechanism or the like. Further, the flat cable 91 is disposed on a horizontal surface of the frame or the like.
The flat cable 91 extends laterally from the carriage 90 substantially along the moving direction of the carriage 90 and subsequently curves back and runs in the opposite direction to the end 92, substantially forming a U-shape. When the carriage 90 reciprocates, the flat cable 91 follows this movement, causing the center position of the substantially U-shaped curved portion to shift. When the carriage 90 moves leftward in FIG. 22, as indicated by two dotted chain line, the radius of the U-shaped curved portion grows larger. When the carriage 90 moves rightward in the drawing, as indicated by a similar line, the flat cable 91 changes shape so that the radius of the U-shaped curved portion grows smaller.
As the radius of the curved portion in the flat cable 91 grows smaller the more the carriage 90 moves to the right, a resilient restoring force generated by the bending of the flat cable 91 also increases. This restoring force acts on the carriage 90, pushing up the carriage so that the carriage 90 floats up from the guide rail (not shown). On the other hand, since the radius of the curved part in the flat cable 91 increases the more the carriage 90 moves leftward, the restoring force generated by the bending of the flat cable 91 decreases so that the carriage 90 no longer floats up on the guide rail. When the carriage 90 floats upward on one end of its range of movement (the right side in this example), the distance from an ink ejection surface on the recording head mounted in the carriage 90 to the recording paper, referred to as the “head gap,” does not remain uniform throughout the range of motion of the carriage 90. This non-uniformity adversely affects the quality of the recorded image.
If the bending rigidity of the flat cable 91 is reduced to resolve this problem, the flat cable 91 cannot maintain its U-shape shown in FIG. 22 and sags downward. As a result, the flat cable 91 can get caught on other components when the carriage 90 reciprocates or otherwise impede this reciprocating motion. Further, even if the flat cable 91 is able to maintain its U-shape, the flat cable 91 easily buckles when coming into contact with other components. These problems have become more magnified as image-recording devices are becoming more compact vertically, thereby reducing the space available for accommodating the flat cable 91 and, hence, reducing the possible radius of the curved part in the flat cable 91.
FIG. 23 shows a conventional structure that includes a supporting member 93 for supporting the flat cable 91 near the carriage 90. A top cover 94 is provided above the supporting member 93 for covering the flat cable 91 from above. A flexible member 95 formed of a sponge material or the like is disposed on the top surface of the supporting member 93 for contacting the top cover 94 with pressure. In this structure, the restoring force of the flat cable 91 generates a force F1 pushing the supporting member 93 upward. However, the top cover 94 generates a force F2 via the flexible member 95 that pushes the supporting member 93 downward, effectively canceling the force F1. Therefore, the carriage 90 does not float.
However, the pressure with which the flexible member 95 contacts the top cover 94 also increases the sliding load on the carriage 90. This increased load is applied on to the motor or other drive source used to move the carriage 90 in a reciprocating motion. As a result, a large motor is required to increase output.
Further, an excessive force F2 applied away from the driving center of gravity of the carriage 90 may act as a rotational moment on the carriage 90, and the sliding posture of the carriage 90 may become unstable as a result.
Further, although the restoring force of the flat cable 91 does not push the carriage 90 over the entire range of movement of the carriage 90, the flexible member 95 contacts the top cover 94 with pressure over this entire range of movement. As a result, an unnecessary sliding load is applied to the carriage 90 during a section of this range of movement.
Further, when the ink supply tubes described above are led laterally from the carriage and extend to the ink tanks, these ink supply tubes may sag downward due to their own weight and the weight of the ink flowing therein. Since many components, such as an encoder strip for detecting the position of the carriage, the guide rail, and conveying rollers, are disposed around the carriage, the sagging ink supply tubes may contact these components. This contact with the ink supply tubes may contaminate or warp the encoder strip, for example, affecting the accuracy of the strip in detecting the position of the carriage. The ink supply tubes may also become damaged by rubbing against the guide rail or the like.